Hi Bruce,
As you probably know the ANAN products are based on HPSDR hardware and software development created by volunteers. The exciter board inside the ANAN-100D – called ANGELIA – uses HERMES hardware design and is equipped with an additional frontend (preamp and ADC). Supplied from a common sampling VCXO coherency is guaranteed. A larger FPGA is also provided to handle the additional data. You can purchase the ANGELIA board for USD 1495.oo at Apache Labs or perhaps at your national dealers. That’s all you need for exciting experiments with diversity to improve SNR in critical conditions. It’s also no big deal to amplify the 500 mW RF power available on the board. Joe, K5SO, wrote a wonderful diversity code implemented in PowerSDR for openHPSDR. We poor guys here in Europe, hi, are using the (older) Altas-based Mercury boards for these experiments, but that’s basically the same hardware only spread over some boards. 73, Helmut, DC6NY Von: Bruce Perens [mailto:br...@perens.com] Gesendet: Sonntag, 6. September 2015 23:05 An: freetel-codec2@lists.sourceforge.net Betreff: Re: [Freetel-codec2] Smoothing the digital cliff (4+4 QAM bitrate peeling idea) Hi Helmut, ANAN-100D provides two phase-coherent receivers in one USD$3500 box, along with a 100W transmitter. The cost is why I didn't bother mentioning it. But obviously we can make a dual SDR receiver for a lot less. Are there any other off-the-shelf hardware solutions today? I have a Hermes and three USRP's on hand, and might also like to experiment with up-conversion for Katena (formerly Whitebox) when we have dealt with higher-priority issues. Thanks Bruce On Sun, Sep 6, 2015 at 1:57 PM, Helmut <dc...@gmx.de> wrote: Polarization diversity is another approach to minimize selective fading we have on the to do list. Our HPSDR environment provides excellent diversity performance. 73, Helmut, DC6NY Von: Bruce Perens [mailto:br...@perens.com] Gesendet: Sonntag, 6. September 2015 21:44 An: freetel-codec2@lists.sourceforge.net Betreff: Re: [Freetel-codec2] Smoothing the digital cliff (4+4 QAM bitrate peeling idea) Any graceful degradation scheme should take into account that the main problem we face is frequency-selective attenuation due to fading. The mechanism, I am told, is multiple depths of reflection from the ionosphere leading to multiple phases combined at the antenna. There is a lot of literature saying that one can actually reduce the fading with circular receive antenna polarization. I've not gotten to test it. If you plan to make this work with conventional antennas, you can experiment with carrier spacing on the theory that some number of carriers would not be in a fade at one time. Thanks Bruce On Sun, Sep 6, 2015 at 9:01 AM, Tomas Härdin <tjop...@acc.umu.se> wrote: Hi (I tried sending this a few days ago but forgot to confirm my subscription to this list - oops! So resending) My name is Tomas and I've been following the development of codec2 on and off for a few years now, and since getting my ham license earlier this year I find myself thinking about it more. A few days ago I had what I thought was a clever idea for fixing the "digital cliff" problem Mike mentioned in a talk that's up on YouTube (I forget which). Today I see on the roadmap post[1] that this is currently being worked on using two GMSK streams, but I thought "hey, maybe someone will find it interesting". So here goes: The idea assumes that codec2 can make use of bitrate peeling. That is, that we can split the stream up into two or more streams where the first one provides a rough but usable quality, and subsequent streams improve upon this. H.264's SVC would be an example from the video world So the idea is take these streams and modulate them onto a hierarchical QAM system. The simplest would be to take the current FDMDV modem and instead of using 14x QPSK (aka 4-QAM) carriers you use 7x 16-QAM carriers. You then code the more important bitstream into the most significant bits in each 16-QAM symbol, and the improvement stream into the lower bits (assuming the two streams have identical bitrate). Since you now have half the number of carriers you can put twice the amount of power into each carrier That's about it. Lots of variants are of course possible, but this should get the point across. I may experiment with the idea once I get some suitable SSB equipment, but for now I'm interested in feedback even if it's just shooting it down :) /Tomas, SA2TMS [1] http://www.rowetel.com/blog/?p=3931 ------------------------------------------------------------------------------ _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2 ------------------------------------------------------------------------------ _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
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